1. Technical Field
The present invention relates to a structure and a manufacturing method for a camera module. More particularly, the present invention relates to a structure and a manufacturing method for a high resolution camera module.
2. Description of Related Art
The portability of mobile phones has brought increased efficiency and convenience to our daily lives. At the same time, continuous improvement in technology has provided mobile phones with more and more functions, including picture taking and video recording for example. In order to meet the requirement for using a high-resolution camera module having advantages of being light, compact, and suitable for mass-production in a mobile phone, the manufacturing process of such camera modules must be effectively simplified, and the module structure must be downsized.
FIG. 1 shows the structure of a conventional high-resolution camera module in cross-section, and FIG. 2 is the flowchart of a conventional method for making a high-resolution camera module. Referring to FIG. 1, a conventional high-resolution camera module 10 includes: a ceramic substrate 11, a glass cover 12, an image sensor chip 13, a packaging portion 14, and a plurality of passive elements 15. As shown in FIG. 2, a method S100 for making a high-resolution camera module includes the steps of: providing a ceramic substrate attached with a glass cover (step S10), providing an image sensor chip onto the ceramic substrate by a flip-chip technique (step S20), and packaging the image sensor chip along its periphery (step S30).
The ceramic substrate 11 provided in step S10 is formed with a hollow portion and has a glass bonding surface 111 and a chip bonding surface 112. The glass bonding surface 111 and the chip bonding surface 112 are the top surface and the bottom surface of the ceramic substrate 11 respectively. The glass cover 12, which is bonded to the glass bonding surface 111, has an upper surface 121 and a lower surface 122. The periphery of the lower surface 122 is bonded to the glass bonding surface 111 such that the glass cover 12 covers the hollow portion of the ceramic substrate 11.
In step S20, the periphery of an upper surface of the image sensor chip 13 is connected to the chip bonding surface 112 by a flip-chip technique while a sensing area of the image sensor chip 13 is aligned with the hollow portion of the ceramic substrate 11, allowing external light to impinge on the sensing area through the glass cover 12. The image sensor chip 13 is electrically connected to the ceramic substrate 11 by conductive elements 16, e.g., solder balls. Thus, a cavity 17 is formed between the image sensor chip 13, the glass cover 12, and the ceramic substrate 11. The height of the cavity 17 is at least greater than the thickness of the ceramic substrate 11. The image sensor chip 13 may be a CMOS image sensor chip.
In step S30, the periphery of the image sensor chip 13 and the joint between the image sensor chip 13 and the ceramic substrate 11 are sealed with a mold compound by an underfill technique or an epoxy dispensing technique. Thus, the cavity 17 is sealed, and the packaging portion 14 is formed. A plurality of passive elements 15 may be additionally provided on the glass bonding surface 111 and be electrically connected to the ceramic substrate 11 by the conductive elements 16.
Nevertheless, the manufacturing method and structure described above have the following problems and limitations. First of all, as the surface of the image sensor chip 13 is not covered and protected by the glass cover 12 until a later stage of the manufacturing process, moisture or dust particles are likely to enter the image sensor chip 13 during manufacture, resulting in a high fraction defective and consequently a low yield rate. Further, the cavity 17 formed between the image sensor chip 13, the glass cover 12, and the ceramic substrate 11 is too large, which not only prevents the camera module from being effectively downsized, but also compromises the stability of temperature cycling tests.